Releasable locking system for a well tool

ABSTRACT

In accordance with an illustrative embodiment of the present invention, a new and improved locking system for locking and releasing parts of a well tool in a well bore is incorporated between members that are movable longitudinally relative to one another. The locking system includes a lock ring having gripping engagement with one member, and cam means that causes the lock ring to grip the member when in one position and movable to another position that enables the lock ring to pass longitudinally therethrough. After passage through the cam means, the lock ring is received within a recess on the other member so that the said other member can move freely along the one member upon disengagement of the cam means.

[ RELEASABLE LOCKING SYSTEM FOR A WELL TOOL Albert A. Mullins, Richmond,Tex.

[73] Assignee: Schlumberger Technology Corporation, New York, N.Y.

[22] Filed: May 26, 1972 [21] Appl. No.: 257,367

[75] Inventor:

[52] US. Cl 166/217, 166/123, 166/134,

166/237 [51] Int. Cl E21b 23/06, E2lb 33/129 [58] Field of Search166/120, 123, 134, 166/135, 237, 238, 216, 217

[56]. References Cited UNITED STATES PATENTS 3,136,364 6/1964 Myers166/120 3,282,342 11/1966 Mott 166/120 3,361,209 1/1968 Edwards t.166/120 3,422,898 l/ 1969 Conrad 166/237 X 3,456,723 7/1969 Current eta1. t. 166/ 120 3,552,489 1/1971 Berryman 166/120 1' July 17, 1973Randermann 166/217 X Primary Examiner-David H. Brown A tt5 Ffiky ifiiesT1i. Archambeall, Jr., David L. Moseley et al.

[57] ABSTRACT In accordance with an illustrative embodiment of thepresent invention, a new and improved locking system for locking andreleasing parts of a well tool in a well bore is incorporated betweenmembers that are movable longitudinally relative to one another. Thelocking system includes a lock ring having gripping engagement with onemember, and cam means that causes the lock ring to grip the member whenin one position and movable to another position that enables the lockring to pass longitudinally therethrough. After passage through the cammeans, the lock ring is received within a recess on the other member sothat the said other member can move freely along the one member upondisengagement of the cam means.

12 Claims, 8 Drawing Figures 111 3,746,093 1451 July 17,1973

United States Patent 11 1 Mullins FIG. 7A

4 Sheets-Sheet l.

F/GIB 59 Patented July 17, 1973 3,746,093

4 Sheets-Sheet 2 Patented July 17, 1973 4 Sheets-Sheet 3 FIG. 5A

RELEASABLE LOCKING SYSTEM FOR A WELL TOOL This invention relatesgenerally to well tools used in well bores, and more particularly to aretrievable well tool that incorporates a uniquely arranged lockingsystem that functions to lock the tool in the set position in the well,the lock system being releasable in such a manner that completeretraction of parts is assured.

In quite a number of well tools such as bridge plugs, packers and tubinganchors, certain parts are moved longitudinally relative to each otherto cause lateral or expansive movement of other parts in order to setthe tool in a well bore. For example, a mandrel might be movedlongitudinally relative to an outer sleeve to cause compression andexpansion of normally retracted packing elements, or relative to anexpander to cause outward shifting of normally retracted slip elements.In order to secure the well tool in set position, one way lock systemsmay be utilized that permit relative movement in one direction butprevent movement in the opposite direction to retain the packing andslip elements in outer positions. Thus the tool is locked in the setposition until such time as it becomes desirable to remove it from thewell.

In order to retrieve the tool from the well, it is desirable to be ableto positively and reliably release the one-way lock systems to enablemovement in the opposite or reverse direction so that the packing andslip elements can return to their normally retracted positions. In thepast, such lock systems upon release incorporated structure succeptableto binding due to friction and other factors, with the result that theslip elements, for example, were only partially released and were unableto return to their fully retracted position. Unless complete retractionis assured, however, difficulty may be encountered in actuallyretrieving the tool from the well intact.

It is the leading object of this invention to provide a new and improvedreleasable one-way lock system for retaining parts of a well tool in setpositions, the lock system being constructed and arranged whereby uponrelease thereof complete retraction of the expanded parts is obtained.

This and other objects are attained in accordance with the concepts ofthe present invention through the provision of a releasable lockingsystem comprising first and second members movable longitudinallyrelative to one another, and a locking means that permits movement inone direction but normally prevents movement in the opposite direction.The locking means incudes a lock member having gripping engagement withthe first member, and a cam means engaging the second member and causingthe lock member to grip the first member when in one position andmovable to another position to enable the lock member to passlongitudinally therethrough. A holding means positions the cam means insaid one position and includes relief means to enable movement of thecam means to the other position, and after passage of the lock memberthrough the cam means the lock means is received within a recess withinthe second member so that free relative movement in the oppositedirection is assured. Such free relative movement enables completeretraction of parts of a well tool to occur without hindrance, so thatthe tool can be readily removed from the well bore.

The present invention has other objects and advantages which will becomemore clearly apparent in connection with the following detaileddescription of a preferred embodiment thereof, taken in conjunction withthe accompanying drawings in which:

FIGS. 1A and 1B are longitudinal sectional views, with portions in sideelevation, of a well packer that incorporates releasable locking systemsin accordance with the principles of the present invention and withparts in the relative positions they occupy during running into a wellbore, FIG. 1B forming a lower continuation of FIG. 1A;

FIGS. 2 and 3 are cross-sections taken on lines 2-2 and 33 of FIGS. 1Aand 18, respectively;

FIGS. 4A and 4B are views similar to FIGS. 1A and 1B except with partsin relative positions when the tool is set in a well casing; and

FIGS. 5A and 5B are views similar to the foregoing except showing theparts in position for retrieving the tool from a well.

Referring initially to FIGS. 1A and 1B for a detailed description of apermanent or retrievable well packer that incorporates releasable locksystems constructed in accordance with the principles of the presentinvention, an elongated mandrel having a full opening throughbore 11carries a set 12 of normally retracted slip elements 13 that aredisposed between an upper expander 14 and a lower expander 15. The lowerexpander 15 is fixed to the mandrel 10 by virtue of being threaded to aring 16 which is threaded to the mandrel, whereas the upper expander 14is movable relatively therealong. A nose piece 17 is fixed to themandrel 10 below the lower expander 15. The slip elements 13 aremaintained in the same horizontal plane by a band 18 that encircles theelements and engages within an inwardly directed recess 19 in each slipelement. Each slip element 13 has spaced upper and lower sets of wickersor teeth 20 and 21, and has inner inclined surfaces 22 and 23 that areengaged by companion outer surfaces 24 and 25 on the respectiveexpanders in order to cause outward shifting of the slip elements inresponse to movement of the upper expander 14 relatively toward thelower expander 15. Each end of each slip element 13 may be provided witha retractor structure including slidable connections to the adjacentexpander so that movement of the upper expander 14 relatively away fromthe lower expander 15 will cause inward movement of the slip elements toretracted positions. For further detail of the slidable connections,attention is invited to Application Ser. No. 57,086, filed concurrentlyherewith and assigned to the assignee of this invention.

The mandrel 10 also carries a packing assembly that comprises severalelastomeric packing rings 31, 32 and 33 mounted around well tubularcompression sleeve 34 that is movable relatively along the mandrel. Theupper packingring 31 is engaged by a downwardly facing abutment 35 thatis fixed to the sleeve 34, and the lower ring 33 is engaged by anupwardly facing abutment 36 that is movable relatively along the sleeveabove an enlarged section 37 thereof provided at its lower end. Ofcourse it will be recognized that movement of the abutments 35 and 36relatively toward one another will cause the packing rings 31, 32 and 33to be compressed and expanded into sealing contact with a wall casingwall.

The lower abutment 36 is coupled to the upper expander 14 through themedium of an intervening sleeve 38. Within limits, the sleeve 38 canmove longitudinally relative to both the upper expander 14 and thecompression sleeve 34. Limited movement with respect to the upperexpander 14 is afforded through the provision of one or more outwardlyextending plugs 39 that are threaded within openings in a reduceddiameter upper section 40 of the expander, and which extend intoelongated slots 41 through the wall of the sleeve 38, whereas limitedmovement with respect to the compression sleeve 34 is afforded bysimilar arrangement including a plug 42 on the section 37 that extendsinto an elongated slot 43 through the wall of the sleeve 34. Of coursethe respective plugs and slots also function to prevent relativerotation of the parts. Moreover, in the initial positions of the parts,the intervening sleeve 38 is relatively fixed by shear pins 44 and 45that extend through the wall of the sleeve and into the enlarged section37 and the upper portion 40 of the expander 14, respectively. With theparts in the runningin position shown in FIG. 1B, the lower end surface46 of the sleeve 38 engages an upwardy facing shoulder 47 on the upperexpander 14 so as to be able to drive the upper expander downwardlyalong the mandrel 10.

A releasable, one-way lock system indicated generally at 50 is disposedabove the upper end surface 51 of the upper expander 14, and between themandrel and the intervening sleeve 38. The lock system 50 includes asplit ratchet or lock ring 52 that normally is surrounded by a split camring 53 which is adapted to be held in an inner position as shown by aninternal locking surface 54 on the intervening sleeve 38. The ratchetring 52 has internal teeth 55 that can mesh with external teeth 56formed, for example, by threads on an adjacent section of the mandrel10. Moreover, the ring 52 has upwardly and outwardy inclined camsurfaces 57 on its outer periphery that are engaged by companion camsurfaces 58 formed interiorly of the cam ring 53. The ratchet ring 52,by virtue of its split construction as shown in FIG. 2, has thecapability for lateral expansion and contraction and can thereforeratchet downwardly along the mandrel teeth 56 in response to downwardforce imposed upon the cam ring 53 by the inwardly directed shoulder 59on the intervening sleeve 38 during downward movement of the latter,however the ratchet and cam rings cannot be moved jointly upwardly alongthe mandrel 10 by the expander 14 due to the camming action of thesurfaces 57 and 58 which causes the ratchet ring to be forced inwardlyand to tightly grip the mandrel. The lock system 50 can be released,however, by moving the intervening sleeve 38 upwardly relative to themandrel 10 and the expander 14 to position an enlarged diameter reliefrecess 60 adjacent the cam ring 53. When this occurs, the cam ring 53due its split or segmented construction as shown in FIG. 2, can expandoutwardly to a throughbore size such that it can pass upwardly over thering 52 without interference therewith. An elongated counterboreprovides an internal annular recess 61 within the upper end section ofthe upper expander 14, and the recess is sized to receive the ratchetring 52 as the upper expander moves upwardly along the mandrel 10.

Turning now to FIG. 1A, it will be seen that the upper abutment 35 isformed in part by the lower end surface of a sleeve extension 65 that isthreadedly fixed to the compression sleeve 34. The sleeve extension 65extends upwardly along the upper end portion of the mandrel 10, and thelower end portion 66 of a releasing sleeve 67 is telescoped over theextension 65. Hereagain, the release sleeve 67 has some capability forlimited vertical movement relative to the extension 65 due to theprovision of opposed stop shoulders 68 and 69 that may be convenientlyformed on the respective member by threads as shown in cut-awayelevation. Relative rotation is prevented by virtue of a plug 70 fixedto the extension and engaging within an elongated slot 71 through thewall of the release sleeve. It will be appreciated of course that therelease sleeve 67 and extension 65 are initially fixed together by meansof a shear pin 72 or the like.

A second releasable one-way lock system 75 is disposed between the upperend portion 76 of the mandrel 10 and the release sleeve 67, and alsocomprises a split ratchet ring 77 (FIG. 3) having internal teeth 78 thatmesh with external teeth 79 on the mandrel. The outer cam surfaces 80 ofthe ratchet ring 77 are engaged by internal cam surfaces 81 formed onenlarged head portions 82 of a plurality of circumferentially spacedspring fingers 83 that depend from the lower end of a latch sleeve 84fitted within the release sleeve 67, the spring fingers being formed byslots 85 that are cut from the lower end of the latch sleeve 84.Normally, the head portions 82 are held inwardly, as shown, by lockingsurfaces 86 and '87 that are formed by stepped diameter inner wallportions of the release sleeve 67. ln a fashion similar to the firstlock system described above, the upper lock system 75 permits therelease sleeve 67 and the extension 65 to be moved jointly downwardlyalong the mandrel 10 as the ratchet ring 77 ratchets over the mandrelthreads 79, however the parts cannot return upwardly due to the coactionof the cam surfaces 80 and 81 and the resultant inward camming action onthe ratchet ring. Consequently, the packing assembly 30 can be lockedwith the rings 30, 31 and 32 in expanded condition and will remain insuch condition until it is desirable to retract them. Retraction isaccomplished through release of the lock system 75 by lowering into thewell an inside grapple type tool that engages the internal threads 88 atthe upper end of the release sleeve 67. An upward pull on the sleeve 67results in shearing of the pin 72 so that the sleeve can telescopeupwardly over the extension 65 and the latch sleeve 84, thus removingthe locking surfaces 86 and 87 from around the head portions 82.Unsupported against outward movement, the head portions 82 are free toresile outwardly so that theycan pass upwardly over the ratchet ring 77,thereby enabling the sleeve extension 65 and the compression sleeve 34to move upwardly along the mandrel l0 and relieve the compressionloading in the packing rings 30, 31 and 32. The extension 65 is alsoprovided by an elongated internal annular recess 89 that is sized toreceive the ratchet ring 77 during such upward movement. Upward movementof the release sleeve 67 along the extension 65 is of course stopped byengagement of the inwardly directed shoulder 68 on the sleeve with theoutwardly directed shoulder on of the extension.

The latch sleeve 84 has threads 90 formed internally at its upper endfor reception of a typical latching mechanism on a seal mandrel (notshown) that forms the lower end of a production string of pipe, anexemplary structure that is suitable for this purpose being shown in U.S. Pat. No. 2,737,248. The presence of a tensile strain in theproduction string will not affect the locked condition of the locksystem 75, since upward force only causes the ratchet ring 77 to gripthe mandrel more tightly. Since the seal mandrel and associated latchingsystem noted above are released by relative rotation, a lock pin 91 onthe release sleeve 67 extends into a groove 92 at the upper end of thelatch sleeve 84 to prevent co-rotation of the latter mentioned part.

In operation, the parts are assembled as shown in the drawings and theassembly is coupled to a conventional gas operated setting tool (notshown) for lowering to the desired setting depth in a well casing. Thesetting tool is releasably connected to the packer throughinstrumentalities including a tension member 100 and an adapter sleeve101 shown in FIGS. 1A and 1B. The tension member 100 includes a centralrod 102 having its lower end connected to a frangible tension stud 103having a reduced neck providing a weak point 104, the lower end of thetension stud being threaded to a bottom cap 105. The cap 105 has acoupling sleeve 106 extending upwardly therefrom, and the couplingsleeve carries a split ring 107 operatively engaged between an upwardlyfacing shoulder 108 thereon and a downwardly facing shoulder 109presented by the lower end surface of the mandrel 10. A holding andreleasing member 110 is received over the upper end portion of thecoupling sleeve 106, and comprises a skirt 1 l1 having an externalannular recess 112 in which the split ring 107 is held. The member 110also includes inwardly directed flange portion 113 that is disposed inspaced relation above an outwardly directed flange 1 14 on the rod 102.Moreover, an upwardly facing shoulder 115 is arranged in verticalalignment with a downwardly facing shoulder 116 on the coupling sleeve106. As long as the tension stud 103 remains intact, the split ring 107is engaged within the annular recess 117 formed in the nose piece 17below the shoulder 109.

The adapter sleeve 101 has a drive surface 120 which engages the upperend face 121 of the latch release sleeve 67. As will be appreciated bythose skilled in the art, activation of the setting tool will causeupward movement of the tension rod 102 and downward movement of theadapter sleeve 101. In response to the resultant movement in oppositelongitudinal directions, the packer is set in the following manner.Inasmuch as the latch release sleeve 67 is in driving contact with theextension 65 of the compression sleeve 34, the compression sleeve andits upper abutment 35 will be shifted downwardly relatively along themandrel 10, which is simultaneously being pulled upwardly. As therelease sleeve 67 and the compression sleeve 34 move downwardly, thelatch sleeve 84 is also driven downwardly by virtue of the shoulderformed by the stepped locking surfaces 86 and 87. As previouslydescribed, the ratchet ring 77 has capability of sufficient lateralexpansion and contraction within the head portions 82 whereby it canratchet downwardly over the mandrel threads 79.

As the compression sleeve 34 moves downwardly along the mandrel 10, theintervening sleeve 38 between the lower abutment 36 and the upperexpander 14 is also moved downwardly, resulting in advancement of theupper expander toward the lower expander which is fixed to the mandrel.Thus the slip elements 13 are shifted outwardly until their teeth and 21bite into and grip the well casing wall as shown in FIG. 4B

to anchor the tool against longitudinal movement. As the interveningsleeve 38 and the upper expander 14 move downwardly, the shoulder 59drives the one-way lock system 50 downwardly along the mandrel 10, andas described above the ratchet ring 52 ratchets along the threads 56 andtraps the extent of downward movement of the upper expander 14. Sincethe ratchet and cam rings cannot be moved jointly upwardly, it will beapparent that the slip elements 13 are locked by the system 50 in set orexpanded positions.

Once the slip elements 13 are set against the casing C, the interveningsleeve 38 and the lower abutment 36 cannot be moved any furtherdownwardly. Consequently, continued downward movement of the compressionsleeve 34 and the upper abutment 35 results in shearing of the pins 44,whereupon the upper abutment moves toward the lower abutment 36 tocompress the packing rings 31, 32 and 33 and expand them into sealingcontact with the surrounding well casing wall. The upper one-way locksystem prevents upward movement of the compression sleeve 34 and therebytraps the packing in expanded condition, whereby the packer is fully setin the casing C.

At a predetermined magnitude of tensile strain in the rod 102, whichmagnitude is somewhat above that required to fully set the packer, thetension stud 103 fails at the weak point 104 as shown in FIG. 4B. Upwardmovement of the rod 102 brings the flange 113 against the holding memberand moves it upwardly relative to the mandrel 10, whereupon the splitring 107 is permitted to resile inwardly and disengage from the recess117. The result is to disconnect the coupling assembly from the mandrel10 as shown in FIG. 4B, whereupon the setting tool is released from thepacker and can be withdrawn from the well. The lower shoulder on the rod102 picks up the member 106 and the cap 105 so that nothing is left inthe well as a result of the setting procedure.

With the packer firmly set in the casing C as shown in FIGS. 4A and 4B,a production string can be lowered into the well and connected to thepacker. A seal mandrel and latch sleeve as referred to above can beconnected to the lower end of the production string, the seal mandrelextending into the bore 11 of the packer mandrel 10 and being fluidlysealed with respect thereto, the latch engaging the internal threads 88at the upper end of the latch sleeve 84 to provide a coupling. Thepacker isolates the producing zone and confines the pressure of theproduction fluids to the production string of tubing that extendsupwardly to the surface.

To release the packer for retrieval to the surface, the productionstring is removed, and an inside grappletype retrieving tool 125 shownschematically in FIG. 5A is lowered into the well on a pipe string andconnected to the internal threads 90 at the upper end of the releasingsleeve 67. A sufficient upward pull on the releasing sleeve 67 willcause the pin 72 to be sheared to enable upward movement of the releasesleeve relative to the mandrel 10 until the shoulder 69 thereon abutsthe shoulder 68 on the extension 65. Such movement removes the lockingsurfaces 86 and 87 from around the latch heads 82, and enables the headsand the fingers 83 to resile outwardly and pass upwardly over theratchet ring 77, which remains stationary with respect to the mandrel10. This permits upward movement of the compression sleeve 34 and reliefof the compression loading in the packing rings 31, 32 and 33 so thatthey will inherently retract. Upward movement of the compression sleeve34 is completely unimpeded, since the ratchet ring 77 is received withinthe recess 89.

When the lower enlarged section 37 of the compression sleeve 34 engagesthe lower abutment 36, the pins 45 are sheared and the interveningsleeve 38 is drawn upwardly relative to the mandrel and to the upperexpander 14. Accordingly, the lock surface 54 is removed upwardly fromaround the cam ring 53 so that it can move outwardly into the recess 60and upwardly over the ratchet ring 52. When the plugs 39 engage thelower ends of the slots 41, the upper expander 14 is pulled upwardlywith respect to the slip elements 13. During upward movement of theexpander 14 the ratchet ring 52, which remains stationary with respectto the mandrel 10, is received within the recess 61 and does not impedesuch upward movement. Movement of the upper expander 14 away from thelower expander results in complete retraction of the slip elements 13 asshown in FIG. 5B. With the packing and the slips retracted, the packercan be retrieved intact to the surface.

It will now be apparent that a new and improved locking system has beenprovided that enables complete retraction of packing and slip elementsafter they have been set in a locked position in a well casing. Inasmuchas the principle locking element, that is the lock ring that grips themandrel, need not be advanced in the reverse direction during retractionof the expanded well tool part, it will be apparent that all substantialbinding action is completely eliminated.

Since certain changes or modifications may be made in the disclosedembodiment without departing from the inventive concepts involved, it isthe aim of the appended claims to cover all such changes andmodifications falling within the true spirit and scope of the presentinvention.

I claim:

1. Apparatus for use in a well tool, comprising: a first member; asecond member movable relatively along said first member; releasablemeans for permitting movement of said second member along said firstmember in one direction but normally preventing movement in the oppositedirection, including a lock member having gripping engagement with saidfirst member, cam means engaging said second member and causing saidlock member to grip said first member when in one position and movableto another position to enable said lock member to pass longitudinallytherethrough, holding means for positioning said cam means in said oneposition and means to enable movement of said cam means to said otherposition; and recess means in said second member for receiving said lockmember after passage thereof through said cam means and during movementof said second member along said first member in said oppositedirection.

2. The apparatus of claim 1 wherein said second member is a slipexpander means that is adapted to shift a normally retracted slip meansoutwardly during movement in said one direction, said expander meansbeing adapted to retract said slip during movement in said oppositedirection.

3. The apparatus of claim 1 wherein said second member is a sleevestructure that is adapted for mounting a settable packing means,movement of sleeve structure in said one direction causing expansion ofsaid packing means and movement thereof in the opposite directionenabling retraction of said packing means.

4. The apparatus of claim 1 wherein said lock member is constituted by asplit ring having internal teeth that mesh with external teeth on saidfirst member to provide said gripping engagement, said ring havingexternal cam surfaces that are engaged by internal cam surfaces on saidcam means.

5. The apparatus of claim 4 wherein said cam means is constituted by asplit cam ring having the capability for lateral expansion andcontraction between said one and said other position.

6. The apparatus of claim 5 wherein said holding means is constituted byan annular member having limited longitudinal movement with respect tosaid second member, said member having an internal annular lookingsurface that engages said cam ring in said one position, said memberbeing movable longitudinally to dispose a relief means opposite said camring to enable movement thereof to said other position.

7. Apparatus for use in a well tool, comprising: a body member, anannular member surrounding said body member and movable relativelytherealong; releasable one-way lock means for enabling movement of saidannular member along said body member in one direction but normallypreventing movement in the opposite direction, said lock means includingan expansible and contractible ring having gripping engagement with saidbody member, cam means engaging said ring and said annular member andcausing said ring to grip said body member when in one position andmovable to another position to enable said ring to pass longitudinallytherethrough; holding means for positioning said cam means in said oneposition and including means to enable movement of said cam means tosaid other position; and elongated recess means within said annularmember sized to receive said ring after its passage through said cammeans and during subsequent movement of said annular member along saidbody member in said opposite direction.

8. The apparatus of claim 7 wherein said ring has upwardly and outwardlyinclined external cam surfaces and said cam means has downwardly andinwardly inclined internal cam surfaces, said cam surfaces beingslidably engaged when said cam means is in said one position anddisengaged when said cam means is in said other position.

9. The apparatus of claim 8 wherein said cam means and said annularmember have oppositely facing transverse surfaces that are engageable totransmit longitudinal forces from said annular member to said cam meansin said opposite direction when said cam means is in said one position.

10. The apparatus of claim 9 wherein said elongated recess means isformed internally of annular member on a diameter at least as great asthe outer diameter of said ring.

11. The apparatus of claim 10 wherein said cam means is formed by thelower end portion of a sleeve having a plurality of circumferentiallyspaced slots cut from the lower end thereof to divide said lower endportion into a plurality of laterally flexible fingers, each fingerhaving an enlarged head portion that is provided with said internal camsurfaces and one of said oppositely facing transverse surfaces.

12. The apparatus of claim 1 1 wherein the upper portion of said sleevehas internal threads therein adapted to be connected with latch means ona seal mandrel extending into said body member.

1. Apparatus for use in a well tool, comprising: a first member; asecond member movable relatively along said first member; releasablemeans for permitting movement of said second member along said firstmember in one direction but normally preventing movement in the oppositedirection, including a lock member having gripping engagement with saidfirst member, cam means engaging said second member and causing saidlock member to grip said first member when in one position and movableto another position to enable said lock member to pass longitudinallytherethrough, holding means for positioning said cam means in said oneposition and means to enable movement of said cam means to said otherposition; and recess means in said second member for receiving said lockmember after passage thereof through said cam means and during movementof said second member along said first member in said oppositedirection.
 2. The apparatus of claim 1 wherein said second member is aslip expander means that is adapted to shift a normally retracted slipmeans outwardly during movement in said one direction, said expandermeans being adapted to retract said slip during movement in saidopposite direction.
 3. The apparatus of claim 1 wherein said secondmember is a sleeve structure that is adapted for mounting a settablepacking means, movement of sleeve structure in said one directioncausing expansion of said packing means and movement thereof in theopposite direction enabling retraction of said packing means.
 4. Theapparatus of claim 1 wherein said lock member is constituted by a splitring having internal teeth that mesh with external teeth on said firstmember to provide said gripping engagement, said ring having externalcam surfaces that are engaged by internal cam surfaces on said cammeans.
 5. The apparatus of claim 4 wherein said cam means is constitutedby a split cam ring having the capability for lateral expansion andcontraction between said one and said other position.
 6. The apparatusof claim 5 wherein said holding means is constituted by an annularmember having limited longitudinal movement with respect to said secondmember, said member having an internal annular locking surface thatengages said cam ring in said one position, said member being movablelongitudinally to dispose a relief means opposite said cam ring toenable movement thereof to said other position.
 7. Apparatus for use ina well tool, comprising: a body member, an annular member surroundingsaid body member and movable relatively therealong; releasable one-waylock means for enabling movement of said annular member along said bodymember in one direction but normally preventing movement in the oppositedirection, said lock means including an expansible and contractible ringhaving gripping engagement with said body member, cam means engagingsaid ring and said annular member and causing said ring to grip saidbody member when in one position and movable to another position toenable said ring to pass longitudinally therethrough; holding means forpositioning said cam means in said one position and including means toenable movement of said cam means to said other position; and elongatedrecess means within said annular member sized to receive said ring afterits passage through said cam means and during subsequent movement ofsaid annular member along said body member in said opposite direction.8. The apparatus of claim 7 wherein said ring has upwardly and outwardlyinclined external cam surfaces and said cam means has downwardly andinwardly inclined internal cam surfaces, said cam surfaces beingslidably engaged when said cam means is in said one position anddisengaged when said cam means is in said other position.
 9. Theapparatus of claim 8 wherein said cam means and said annular member haveoppositely facing transverse surfaces that are engageable to transmitlongitudinal forces from said annular member to said cam means in saidopposite direction when said cam means is in said one position.
 10. Theapparatus of claim 9 wherein said elongated recess means is formedinternally of annular member on a diameter at least as great as theouter diameter of said ring.
 11. The apparatus of claim 10 wherein saidcam means is formed by the lower end portion of a sleeve having aplurality of circumferentially spaced slots cut from the lower endthereof to divide said lower end portion into a plurality of laterallyflexible fingers, each finger having an enlarged head portion that isprovided with said internal cam surfaces and one of said oppositelyfacing transverse surfaces.
 12. The apparatus of claim 11 wherein theupper portion of said sleeve has internal threads therein adapted to beconnected with latch means on a seal mandrel extending into said bodymember.